Demand for food having a low cholesterol content has been increased not only as a diet for treating patients with arteriosclerosis, but also as health food for normal healthy people. In this respect, although eggs are excellent food, they contain a large amount of cholesterol. Therefore, it is requested to reduce the cholesterol content of eggs.
As means for reducing a cholesterol content of food, direct extraction of cholesterol with various solvents has been proposed. For example, solid-liquid extraction of cholesterol contained in liquid or powdered egg with an organic solvent has been known. Examples of this extraction are disclosed in Japanese Patent Kokoku No. 46-42944 and Japanese Patent Kokai No. 47-19062. However, there are various disadvantages in the above extraction with an organic solvent. For example, since cholesterol is normally extracted together with other fats and oils, the resulting food product has a very low fat and oil content. Particularly, in liquid or powdered egg, triglycerides, pigments and the like are extracted together with cholesterol and, therefore, its characteristic flavor is lost, which results in deterioration of its commercial value. Further, there is the possibility that a remaining solvent influences on the human body. Therefore, it is hardly at best questionable to say that the above extraction is suitable for practical use.
Japanese Patent Kokoku No. 62-51092 proposes a process for removing cholesterol from powdered egg by contacting powder egg with supercritical CO.sub.2. However, since powdered egg itself has extremely inferior flavor in comparison with that of liquid egg, there is a disadvantage that the use of the resulting egg product is limited.
Heretofore, extraction of various organic materials with a supercritical fluid has been known and practical examples thereof include decaffeination of coffee, extraction of hop extract and the like. However, it has been considered that extraction with a supercritical fluid would be ineffective for extraction of a substance from a material containing a large amount of water such as liquid egg.